A steel plate for a home appliance of the related art was manufactured by post-processing a PCM steel plate or performing powder coating on a PCM steel plate after processing the PCM steel plate. However, because of the trend toward classy home appliances and the improvement in living standards of consumers, color differentiation by ink printing and diversity of gloss is pursued instead of the existing single color tone of PCM and a powder coated panel, and thus, a PCM laminating coating manner for meeting the needs has been widely used.
As such, a laminate attached to an iron plate by the PCM coating method allows excellent gloss and does not require separate ink printing, as compared with a paint coating system. However, since the laminate is attached by using only an adhesive, the laminate has poor adhesion to materials as compared with a case of using the paint, and home appliances may be problematic in main physical properties. For example, durability such as corrosion resistance, water resistance, or the like, may be degraded in the home appliances. Also, a laminate film has a thickness of 150 to 160 μm, and this is thicker than a coating thickness of the paint, 25 to 35 μm, resulting in a high price per area, which gives rise to an extreme price rise burden for classy home appliances. Also, since the laminate film itself is printed with ink, it is difficult for coating companies and electronic companies to manage designs on their own. Above all things, the cause of human deaths in a recent big fire lies in poisonous gas and a large amount of smoke, which are generated at the time when surrounding furniture and home appliances are burning, and these make it fail to find escape ways, resulting in extensive damage.
Among the above problems, in order to meet the needs for classy products by customers, there is an attempt of a coating by a 4-coating-3-baking system, of which coating of a transparent paint is performed in a wet-on-wet manner by installing ink-printable facilities in a coating line. An ink printing system allows coating on a thin film, as compared with a laminated film, improves coating physical properties by a system of bottom coat paint-base paint-ink-transparent paint, and ensures economic feasibility. Korean Patent Laid-open Publication No. 1998-059115 (Patent Document 1) discloses a polyester paint composition prepared by employing a coating method using a 4-coating 3-baking system.
However, the existing resins can not attain a low smoke density at the time of firing, and measures for ensuring adhesion and durability of the paint cannot be developed.